Thats perfectHow long to veg your plants is somewhat of a personal choice. Plants tend to double or triple in size during the flower stage, so some people may need to put their plants into flowering earlier in order to prevent any height issues during flowering.
Ideally you would wait until the plants have alternating nodes before putting them into flowering.
You can veg a plant as long as you would like though. Many people will keep a mother plant in a vegetative state for many months in order to take clones from her - and put her into flowering at a much later date.
Yield can also be a factor in deciding when to flower your plants. The longer a plant is in vegetation the more growth you will gave, and therefore the more yield you will get.